Cloned human 5-HT1A receptor pharmacology determined using agonist binding and measurement of cAMP accumulation

Twenty agonists and nine antagonists were evaluated for their ability to compete for [3H]-8-hydroxy-2-(di-n-propylamino)tetralin ([3H]-8-OH-DPAT) binding to the cloned human serotonin-1A (ch-5-HT1A) receptor expressed in Chinese hamster ovary cells and for their ability to alter adenylyl cyclase activity in the same cells. The most potent full agonists of high affinity included N,N-dipropyl-5-carboxamidotryptamine (pEC50 = 9.6 ± 0.1), MDL 73005EF (pEC50 = 9.3 ± 0.2), 5-methyl-urapidil (pEC50 = 9.2 ± 0.1), 5-carboxamidotryptamine (pEC50 = 9.1 ± 0.2), R(+)-8-OH-DPAT (pEC50 = 8.6 ± 0.1) and BMY-7378 (pEC50 = 8.6 ± 0.1). WB-4101 (pEC50 = 8.3 ± 0.2; IA = 79%), clozapine (pEC50 = 8.1 ± 0.3; IA = 29%), (buspirone (pEC50 = 7.6 ± 0.2; IA = 79%), quipazine (pEC50<5; IA = 45%) and R-DOI (pEC50<5; IA = 31%) were weaker agonists with partial agonist properties. The most potent antagonists were WAY-100,635 (pKi = 10.2 ± 0.1), methiothepin (pKi = 8.8 ± 0.2), spiperone (pKi = 8.7 ± 0.2) and NAN-190 (pKi = 8.5 ± 0.2). The receptor affinities and functional potencies were well correlated (r = 0.88; P<0.0001). Our binding data correlated well with the pharmacology of endogenous 5-HT1A receptors in the rabbit iris-ciliary body (r = 0.91; P<0.001) and rat hippocampus (r = 0.93, P<0.0001). Our functional cAMP data correlated well with other cAMP accumulation data (r = 0.8, P<0.01 vs calf hippocampus) but less so with [35S]-GTP-yS binding to the ch-5-HT1A receptor as a functional activity read-out (r = 0.58, P<0.05). The present study provides a detailed pharmacological characterization of the ch-5-HT1A receptor using binding and functional assays.